The present invention relates to a device for feeding combustion air into a battery of coke ovens, said device allowing for an even and efficient feed of air to these coke ovens in the area above the oven door opening or in the upper door area and wherein the air feeding device in the oven wall above the door area or in the upper door area is supported by air feeder ducts through the oven top that are provided with an adjusting device for controlling the gas flow, which is not exposed to the high temperatures that usually prevail on coal carbonization and oven charging. The present invention also relates to a method for coal carbonization with the improved air feeding system.
Heating of non-recovery or heat recovery ovens is usually effected by combustion of gas evolving on coal carbonization. Combustion is so controlled that part of the gas is burned above the coal charge with primary air in the oven chamber. This partly burned gas is supplied through ducts, which are also designated as downcomer-channels, to the heating flues in the oven chamber sole and completely burned here by addition of further combustion air, i.e. secondary air.
In this manner, heat is supplied to the coal charge directly from the top and indirectly from the bottom, taking an advantageous effect on the carbonization rate and thus also on the oven performance rate. To carry out the method it is required to exactly measure the supplied primary air and secondary air and to control these variably during the coking time. In prior art technology, flat-type “heat recovery” and “non-recovery” coke ovens have been extensively described. For example, reference is taken to U.S. Pat. No. 4,344,820 A, U.S. Pat. No. 4,287,024 A, U.S. Pat. No. 5,114,542 A, GB 1555400 A or CA 2052177 C.
To implement the method, several ovens charged one after another to bridge the time of the coal charging procedure are usually operated at the same time. When operating several ovens, these ovens are generally built in a series adjacent to each other. In designating combinations of ovens, it is general practice to designate a combination of several coke ovens of the “non-recovery” type or “heat recovery” type as an “oven bank”. A combination of conventional coke ovens, however, is called an “oven battery”.
According to the conventional state of the art in technology, primary air is aspirated from the atmosphere through openings in the doors. Secondary air is aspirated through openings in the bottom plinths of the coke oven chambers and passed via channels into the heating flues which essentially extend horizontally under the coke oven chamber. The openings for primary and secondary air are either opened permanently or provided with adjustment devices to regulate the amount of air to be aspirated.
In operation of coke ovens, it is found that the coke ovens are charged with air in different intensities, depending on the prevailing weather conditions, thus leading to inhomogeneous combustion and a deterioration of the reproducibility of the cokemaking process. With stronger winds, the combustion velocity in the environment of the door rises substantially, while only incomplete combustion is achieved at a slower air velocity. Moreover, combustion achieved in the upper part of the oven is inhomogeneous only. For this reason, openings above the door area would yield a substantial benefit. Openings in this area, however, are difficult to provide because the design and construction of the door area stands in opposition to implementing openings above the door area.
In general, coke oven batteries are operated cyclically. A typical cokemaking cycle generally takes 20 to 96 hrs, whereupon the coke push is taken out from the coke oven chamber on completion of the cokemaking process. It is passed on for further processing, and the coke oven chamber is charged again without being subjected to a cleaning procedure. For this purpose, the coke oven chamber doors existing on either side of the oven are opened and the interior of the coke oven chamber is emptied towards the other side, using a pusher ram. This procedure basically takes just a few minutes. Access to the interior of the coking chamber is afforded by opening the oven doors which are moved to a position above the oven opening to allow for executing the charging procedure. The doors remain in this position for the period of coal charging.
An oven door is usually made of metal and has a thickness of several centimeters. Therefore, the oven door heat up substantially in the course of the cokemaking process. When it is moved into the position envisaged for the charging procedure, the external wall of the oven chamber lying above the oven door heats up very much, because the distance of the door from the oven chamber when being in the charging position is only very small. Existing adjustment devices for the amount of supplied primary air which are located in this area can therefore be deformed due to strong heat. They must then be renewed after some charging cycles. This involves added cost. Moreover, a deformation of the adjustment device would cause it not to be able to perform its regulating function adequately. The consequence is an uneven cokemaking process and a coke product that is marked by worsened quality.